# User talk:Gandalf61

## LEO III computer

Why do you persist in removing the deletion of a grossly misinformed reference in the LEO computer page, when a cursory examination of Wikipedia's own material on the subject would reveal its inadequacy? Are you drunk on your editorial power? Too lazy to check the facts? Incompetent? — Preceding unsigned comment added by 212.166.149.54 (talkcontribs)

Your edits are contradicting the reference given in the article. You need to provide a reference to a source that confirms your version. The onus is on you to provide evidence that supports your edit - see our policy on verifiability. You should also read and take note of our policy on no personal attacks. Gandalf61 (talk) 10:49, 25 January 2013 (UTC)

I have, repeatedly, supplied a source that confirms the edit you complain about above, and deleted the link supported by you as a "verifiable" source. The later is "verifiable" only by a strange misuse of language, since it is demonstrably false; and yet you persist in restoring it:

1. It claims that GEC made System 4 computers: false, see System 4.

2. It claims that the 2900 mainframe was "emulating an ICL 1900 mainframe, emulating a GEC System 4 mainframe emulating a LEO": false, see the referenced paper, Morgan, Tony (2012), "THE DME LEO DME STORY" which clearly states that the LEO emulation was written in ICL 2960 microcode. I personally know this to be true, having met the engineer who wrote it in Dalkeith, and having discussed it with him, in 1980.

3. System 4 emulation on a 2900 did not run under 1900 emulation: all three of the 1900 Series, System 4, and Leo, emulations were implemented in 2900 microcode. All of them ran directly on the 2900 hardware in one of its emulation personalities. See CME.

The source that I have supplied, on the other hand, is a paper published by the LEO Computer Society. This is a society founded by former LEO implementors, programmers and users, and is dedicated to preserving the history of these early British computers. Its quality and provenance are unimpeachable.

Will you now stop polluting this article with a reference to a largely fictitious blog posting that quotes a faulty reminiscence at third hand? — Preceding unsigned comment added by 77.102.138.129 (talk) 15:29, 31 January 2013 (UTC)

Now that you have explained why you want to remove the original reference, I am happy not to restore it. All you had to do was explain your objections to the source. Repeatedly deleting a long-standing source from an article without any explanation looked like vandalism. Next time, try more explanation and less drama. A little more politeness would not go amiss either. Gandalf61 (talk) 22:04, 31 January 2013 (UTC)

## thanks

for your answer about a black hole in a neutron star. I appreciate the actual calculations you did(which no one else did). Next weekend I'll hopefully have time to trace thru your derivation and learn something real. Rich76.218.104.120 (talk) 05:57, 16 April 2013 (UTC)

No problem. It was an interesting question. Gandalf61 (talk) 09:53, 16 April 2013 (UTC)

## Any Thoughts ?

Wikipedia:Reference desk/Archives/Mathematics/2013 July 6#Convergence and Closed Form Expression. — 79.113.214.209 (talk) 22:44, 18 July 2013 (UTC)

It's an interesting question, but I don't have any ideas about it. Gandalf61 (talk)
Same here, LOL! Thank you for taking the time to think about it. :-) — 79.113.210.34 (talk) 02:11, 20 July 2013 (UTC)

## zero per zero

You do not understand the formal mathematics behind the division relation.

Definition: Let $m$ and $n$ be integers. We write $m \mid n$, and say that $m$ divides $n$, if and only if there exists a $k$ integer such that $mk = n$; otherwise, we write $m \not\ \mid n$.

Examples:

$6 \mid 30$, because $6 \times 5 = 30$.
$14 \mid 0$, because $14 \times 0 = 0$.
$0 \mid 0$, because $0 \times 12345 = 0$; additionally, $0 \times 999 = 0$.
$0 \not\ \mid 4$, because for any $k$ integer, $0 \times k = 0 \ne 4$.
$2 \not\ \mid 3$, obviously.

Definition: Let $m$ and $n$ be integers. If there exists a unique $k$ integer such that $mk = n$, then we write $n / m$ and say $n$ per $m$ (or $n$ over $m$) to refer to this $k$, and call this the result of dividing $n$ by $m$. (If there is no such $k$ or it is not unique, then we do not define $n / m$).

Examples:

$30 / 6 = 5$, because $6 \times 5 = 30$, and $6 \times k_1 = 30$ and $6 \times k_2 = 30$ imply
$6 \times k_1 - 6 \times k_2 = 30 - 30$,
$6 \times (k_1 - k_2) = 0$,
$k_1 - k_2 = 0$, and
$k_1 = k_2$.
$0 / 14 = 0$, by similar reasoning.
$4 / 0$ is not defined, because $0 \not\ \mid 4$.
$3 / 2$ is not defined, because $2 \not\ \mid 3$. (However, $3 / 2$ is defined on real numbers).
$0 / 0$ is not defined, because both $0 \times 12345 = 0$ and $0 \times 999 = 0$.

The last example shows why, despite the fact that $0 \mid 0$ (zero divides zero), $0 / 0$ (zero per zero (or zero over zero), the supposed result of dividing zero by zero) is not defined: because neither definition is any better than any other ($0 / 0 = 12345$ vs $0 / 0 = 999$).

It is consistent to say that

• zero divides zero, but
• zero per zero (or zero over zero) is undefined.

It is not consistent to say that

• the definition of divisible goes as given above, but
• zero does not divide zero. — Preceding unsigned comment added by 81.182.160.107 (talk) 12:19, 1 August 2013 (UTC)
I understand your reasoning, but I guess it comes down to a question of convention. I have raised this question at Wikipedia talk:WikiProject Mathematics to determine consensus and see if anyone can provide a reliable source on this. Gandalf61 (talk) 12:50, 1 August 2013 (UTC)

## Ben Loyd-Holmes

I agree with your removal of peacock terms (that was on my list to do), but I have reverted the image back to the cropped version (and the proper ibox parameters).--ukexpat (talk) 15:56, 1 August 2013 (UTC)

No problem. I didn't intend to change the image - I must have somehow edited the last-but-one version by mistake. Gandalf61 (talk) 15:59, 1 August 2013 (UTC)

## Hatting

No big deal, and thanks for fixing. The reason I did that was (1) I realized I was giving something close to medical advice, after (2) being told that such tests are not necessarily reliable; and (3) in order to give some context to that followup statement, just in case someone was curious. Otherwise I would simply have deleted it. :) ←Baseball Bugs What's up, Doc? carrots→ 14:43, 25 October 2013 (UTC)

I should say not necessarily reliable. They work for me, but they might not work for someone else, and no conclusions should be drawn either way. ←Baseball Bugs What's up, Doc? carrots→ 14:44, 25 October 2013 (UTC)

## Logarithm article

Hi Gandalf61!

About the Characterization of the logarithm function as essentially the only function that transforms products into sums: If you feel that it is unnecessarily lengthy, why not try and shorten it? What you cannot do, in my opinion, is just to put it in "Generalizations/Related concepts", because it is neither a related concept, nor a generalization, is an _important_, _fundamental_ property of the logarithm.

Regards! Jose Brox (talk) 13:19, 28 October 2013 (UTC)

We are debating in the Talk:Logarithm page about my polemic subsection, I thought you may be interested on it. I tried to propose a better and more comprehensive content for it. Jose Brox (talk) 14:26, 29 October 2013 (UTC)

## Knapsack problems

Hi, I saw a note and edits from you back in 2009, regarding whether a Knapsack variation was a change making problem (it wasn't). Here, Talk:List_of_knapsack_problems, I ask if I have a change making problem description correct. Would appreciate a comment/confirmation. Thanks, goodeye (talk) 19:28, 18 November 2013 (UTC)

I have replied at Talk:List_of_knapsack_problems. Gandalf61 (talk) 08:55, 19 November 2013 (UTC)

## Mycoplasma genitalium

I see you talked about this before it has 525 genes, I also saw this number in New Scientist. But Wikipedia article "recorded" it is 521 genes. So which 1 is correct? K. M. (talk) 03:23, 20 November 2013 (UTC)

I don't know which is correct. You could raise this at the article's talk page, or at the Science Reference Desk. Gandalf61 (talk) 10:31, 20 November 2013 (UTC)